Actual printing ink can have a unique odur that maybe isn't what I would call desirable. And maybe with a combined damp that it looks to have, then maybe thats the smell (or some of it).
I did grab a few things back in the "Christmas All The Anime" sale and they did have slight damp effect (but no really odur that I rememeber), but no where near that bad.
I did manage to sort mine by taking them out (of the case) putting them on a flat surface and then leaving them under a large flat weight (so in my case 10 thick heavy books)
But I think that level of crinkling/damp might be a bit too much. And fixing it may not actually help you if you intend to return.
I'm not too familiar with re-sealing but I would expect All the Anime/ Gurren Laggan to have orgianlly been in that crinkly cellophane which at the top and bottom are just folded in.
I don't think that how re-sealing would have been done, but I have not tried it so have no idea of the process/ final results.
But either way I would like to think the seller would have noticed this damp effect on the cover (and as Denny mentioned they have verified that they were probably aware of it as it happened during manafacturing). And I would like to hope they would then actually mention this in the listing. If it is mentioned on the listing might be a bit harder, but still not impossible.
But yeah I would go with what Denny is suggesting and see if you can get a solution